Decontamination devices have typically been designed to filter, irradiate, and/or trap irritants or infectious agents, such as bacteria, viruses, mold and other microorganisms, in air. Such irritants and infectious agents may contaminate the air due to industrial accidents, fires, an infected individual, or a chemical or biological terrorist attack, for example. Decontamination devices typically comprise a chamber to expose contaminated air to ultraviolet (“UV”) radiation followed by a filter. The filter may be a high efficiency particle arrester (“HEPA”) filter.
Ultraviolet irradiation in prior art devices is typically unable to sufficiently penetrate the filters to kill trapped biological agents. Many biological agents, such as mold and bacteria, can grow on most filter media. The filter media, including such mold and bacteria, as well as trapped viruses, may thereby become a source of contamination and infection. Since some deadly viruses and bacteria can survive for extended periods of time in filters, removal of the contaminated filters may release the very contaminant the decontamination unit was intended to contain. For example, they can cause infection of a person replacing the filter or conducting maintenance on the decontamination device. They may also become a source of infection of people in a room with the device.
In many of these devices, ultraviolet irradiation alone may not provide sufficient decontamination because the contaminated air is not exposed to the radiation for a sufficient time to kill the biological agents. High energy ultraviolet irradiation, such as ultraviolet germicidal irradiation in the wavelength range of 2250-3020 Angstroms (“UVGI”), has been used to irradiate filters but UVGI alone may still not adequately destroy biological agents caught within the filter because in the prior art configurations, the biological agents are not exposed to UVGI irradiation for a sufficient time, and the UVGI irradiation may not adequately penetrate the filter.
U.S. Pat. No. 5,330,722 to Pick et al. (“Pick”) provides a UV lamp to expose a surface of a filter to UV irradiation, as the UV lamp and filter are moved with respect to each other. The UV lamp is only exposed to a portion of the filter at any given time. This design may not allow for an adequate germicidal effect upon agents that may pass through portions of the filter that are displaced with respect to the UV lamp. Although Pick suggests providing a UV lamp that is also capable of producing germicidal levels of ozone that can pass through the filter, the ozone and UV are still unable to destroy agents passing through portions of the filter that are not exposed to the UV lamp. Since agents passing through the filter are returned to the air, filtration of the air may be inadequate.
To improve the germicidal effect in a filter, filters have been coated with germicidal agents. For example, in U.S. Pat. No. 5,766,455 to Berman et al., the filter is coated with metal oxide catalysts that are activated by UV light to degrade chemicals and biological agents. Because this requires modifying filters with a metal oxide catalyst slurry, the filters have added expense and require an additional step of quality control to verify that the dynamics of the filter, such as size of particles trapped and maximum air flow, have not been altered.
Isolation rooms, isolation chambers and isolation areas in hospitals, laboratories and manufacturing facilities may filter contaminated or potentially contaminated air and vent the filtered air to a safe area. As above, the filters may become dangerous sources of infection and have to be collected and disposed of accordingly. Mobile isolation units are also known, enabling the expansion of isolation zones in hospitals to facilitate the handling of diseased patients, for example. However, mobile isolation units draw significant amounts of air into the unit, potentially exposing patients to further infection. Since antibiotic resistant strains of bacteria and fungus may be present in hospitals, these isolation units may be dangerous to immune or respiratory compromised patients.
Improved decontamination units and isolation devices are needed to better address typical contamination situations in industrial and medical applications, for example, as well as increasingly dangerous threats posed by antibiotic resistant strains and terrorism.